Olloclip is a slide-on lens system for the iPhone. There are several options available – with each setup offering multiple lens options in a single unit. There are fisheye, macro, telephoto and polarizer options available. For example, the 4-in-1 for the iPhone 5/5s features a fisheye & wide angle lens on one side and a 10x and 15x macro lens on the other.
The lenses work pretty simply by sliding onto the corner of your specific iPhone model. Lenses are available for the iPhone 4/4S and iPhone 5/5S and range in price from about $70 to $100.
The lenses don’t add a whole lot of bulk; however, it’s not something I want to leave attached to my iPhone all the time. That said, they are small enough to fit in your pocket if you want to have them at the ready for mobile shooting.
The biggest downside I noticed is that they don’t work with any case except the case made by Olloclip, which has a section that slides off the corner of the phone where the rear camera is at. This allows you to mount the lens unobstructed on the iPhone.
Additionally, the Olloclip case has options mounting systems for cold shoe attachments like external lighting and tripod adapters.